“He soaks in the sunshine…and I realize that he is mine,” Underwood wrote alongside the snap, which shows Isaiah in an Under Armour t-shirt and black shorts looking up at the sky and smiling while seated on a deck.

“I don’t deserve such sweetness!”

For good measure, she added some sun emojis and the hashtags “#Blessed” and “#MomLife.

Underwood has been open about her journey into motherhood, tellingPEOPLE last October that she wants to raise her son to “have a loving heart toward people who are different.”

“Mike and I talk about teaching him how to approach everybody in a loving way, even if they’re not the same, and to try to say, ‘You know what? God loves them, so it should be my job to my best to love them as well,’” Underwood added.